<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var num = Number(prompt(''));
if(num > 90 && num <= 100){
    console.log('优秀');
}
else if(num > 80 && num <= 90){
    console.log('良好');
}
else if(num > 70 && num <= 80){
    console.log('中等');
}
else if(num > 60 && num <= 70){
    console.log('及格');
}
else{
    console('不及格');
}
    </script>
</body>
</html>